Known as Turtle, the world's first military submarine appeared during the American War of Independence. It was 10 feet long, constructed of two wooden shells covered with tar, propelled by a one-person crew using hand-cranked propellers, had enough air for a 30 minute dive and its weapons were a drill, a keg of gunpowder and a time fuse. Fast forward 230-odd years to the British Navy's Astute class submarine, which is currently undergoing sea trials, and you get a very different picture. Made up of a million individual components and capable of carrying 93 crew and an array of weapons including Tomahawk cruise missiles, the nuclear-powered Astute class is 97m long, weighs 7,800 tons, is coated in 39,000 sonar masking acoustic tiles and doesn't need refueling throughout its expected 25 year service life.

The first of the BAE Systems built Astute Class subs (called Astute, with the three further vessels under construction called Ambush and Artful and Audacious) joined the Royal Navy’s second Type 45 destroyer Dauntless in the firth of Clyde for trials this week.

The attack submarine is designed to cover several bases, from anti-ship and anti-submarine operations to surveillance and intelligence gathering and support for land forces. It has a 50% greater weapons load than Trafalgar (S&T) Class in service at present, is stealthier than any other submarine previously operated by the Royal Navy and packs in a staggering amount of technology. This includes the the world's most advanced attack sonar suite - Sonar 2076 - that has the processing power of 200,000 laptop computers and can detect ships on the opposite side of the Atlantic. A sophisticated digital optical mast provides 360 degree infra-red and thermal imaging and replaces the traditional periscope and all-in-all, BAE Systems says five million lines of software code have been written to control of the vessels complex systems and 100 km of cable run through its hull - a process made easier by a modular construction system.

The Astute travels at 30 knots underwater and will soon attempt to dive to it's maximum depth of 300 meters as part of the current trials. Although it has enough power to last 25 years, the patrol endurance is slated at 90 days... and we still don't envy the submariners on that stretch. The sea-to-land Tomahawk cruise missiles can be delivered with accuracy over a 2,000 km range and Speafish Torpedoes also form part of the Astute's arsenal.

Three Astute Class subs have been officially ordered by the Royal Navy and a fourth is well underway. The program, which began in 1997, is not alone in having suffered lengthy delays, and doubts have been expressed whether the seven submarines BAE hopes to build will eventuate - something to do with the GFC and a £1.2 billion price tag apparently.

BAE Systems via Daily Mail.